This invention concerns a transfer for decorating surfaces, preferably textiles or other flexible materials, with images being extremely durable and capable of standing both hot water wash and dry cleaning. In particular the invention concerns a transfer for decorating surfaces with images comprising light-reflecting areas of any configuration and colour in arbitrary combination with coloured non-reflecting areas. The invention also relates to a process of making such transfer.
It is known to decorate textiles by printing patterns in various colours by a suitable printing method, e.g. the silk screen process. For such patterns to be durable in use and to have good fastness to repeated washing, it is important that the inks used for the printing have good adhesion and cannot be peeled or picked off, that they are elastic so as to be capable of following the expansion and contraction of the substrate, and that they do not crackle or flake.
So-called plastisol inks have been developed for this purpose, based on elastomeric resins, often modified polyvinyl chloride (PVC), dissolved in high-boiling organic solvents. These plastisol inks, which are also called gum printing inks, can be given all possible shades by pigmentation.
It is also known to produce so-called transfers by means of these plastisol inks, i.e. by printing a given pattern in mirror-inverted fashion on a suitable substrate, preferably silicone or wax treated paper. The pattern may then be transferred by the user, e.g. a textile factory, from such a transfer to the textile by application of heat, i.e. the transfer is placed with the inked side against the textile and heated to 130.degree. to 200.degree. C., generally 160.degree. to 180.degree. C., under a pressure of 100 to 800 kPa, generally about 500 kPa, for 10 to 30 seconds, generally 15 to 20 seconds. The temperature, pressure and treatment time used depend, of course, upon the type and nature of the textile fabric and upon the plastisol type applied, but generally higher temperatures will involve treatment for a shorter period of time, and vice versa.
The international patent application published as WO 80/00462 describes a method of applying a metallised and/or pigmented decoration to a surface, for example a garment surface, comprising the steps of first providing a conventional ink transfer having the form of the intended decoration, and transferring the image therefrom to the surface in conventional manner by application of heat and pressure, and then superimposing a foil having a metallised and/or pigmented coating to the said image, subjecting the foil to heat and/or pressure to cause it to adhere to the image, and peeling off the foil thereby to provide a metallised or pigmented cover adhering to the image and being coextensive therewith. The metallised or pigmented coating on the foil may optionally be provided with a layer of heat or pressure sensitive adhesive on the face intended for application to the image, being so selected as to have an affinity for the material of the image and a disaffinity for the surface to which the image is applied. The metallised and/or pigmented coating may also include a cover layer on the face opposite the face intended for application to the image. But in any case this so-called "hot split" method only aims at applying a metallised and/or pigmented coating to the entire surface of an image being already transferred conventionally from a known transfer.
It is further known to produce so-called retro-reflecting films with a great light reflecting capacity for application on e.g. textiles, first and foremost for security reasons. These retro-reflecting films or reflex films come in two main types, one with a very large number of fine glass beads with a high refractive index embedded with a reflecting substrate in a base sheet (glass bead type), and another formed with a large number of prisms in a sheet. Both types may be formed with the glass beads or the prisms exposed in the surface (open type) or enclosed in a transparent layer (semi-open type) or coated with an optionally inked layer (closed type), or finally encapsulated in closed cavities with entrapped air (capsule type). The reflex films may be formed as reflex transfer films with a heat-activated adhesive intended for i.a. heat application to textiles. Reflex transfer films of the glass bead type may moreover be produced in a very elastic material, which makes them particularly suitable for application to flexible materials.
It is known from i.a. U.S. Pat. No. 3,836,227 to produce such a retro-reflecting film of the glass bead type by embedding a monolayer of glass microspheres having diameters between about 40 and 80 .mu.m to a depth of about 40% of their diameter in a carrier sheet consisting of a polyethylene coating on a paper liner with heating of the polyethylene to about 140.degree. C. A transparent specular coating of zinc sulfide having a thickness of one-quarter the wave length of white light is vapor-coated onto the exposed surfaces of the microspheres, whereafter the exposed glass microspheres are coated with an aqueous dispersion of a binder material comprising a thermoplastic heat-activatable adhesive copolymer of ethylene, vinyl-chloride and acryl amide and optionally a further thermoplastic heat-activatable adhesive copolymer of methyl methacrylate, ethyl acrylate and methacrylic acid in sufficient thickness to leave a dried layer which completely covers the microspheres. The layer is dried at 93.degree. C. for 10 min. Optionally, a second layer comprising a thermoplastic heat-activatable adhesive copolymer based on acrylic acid and an acrylic acid ester may be applied. The resulting sheet material may be adhered onto a substrate, such as cardboard, by placing the exposed surface of the binder layer against the cardboard, and then passing the combination momentarily between hot lamination rolls heating the interface of the binder layer and cardboard to 120.degree.-132.degree. C. When the laminate has been cooled to room temperature the polyethylene-coated carrier sheet is stripped away.
It has been a significant drawback in the use of the known reflex transfer films that when applying the reflecting figures and signs, e.g. in the form of letters (words, messages) and logos it has been necessary to punch or cut out each individual letter/figure and apply them manually. Even though substantial funds have been invested in computer controlled cutting machines it has been necessary to remove the excess material around and in the letters manually, which is both labour demanding and entails heavy material loss. It is another drawback that previously it has only been possible to produce single-coloured lengths of reflex transfer films. True, it is known to print a reflex transfer film with transparent colour over the glass bead surface to obtain various patterns and light effects, but this method does not either provide the possibility of producing individual letters/figures without the use of punching or cutting.
An attempt to remedy some of these drawbacks has been made in DK patent No. 155 888 B (and the corresponding international patent application published as WO 88/08793) according to which a special plastisol reflex transfer is prepared by a method in which a conventional plastisol transfer is coated with an elastomer granulate of a type (e.g. based on polyacryl amide) compatible with the plastisol ink and with the surface layer of a reflex transfer film, and the granulate is fused into the plastisol print by heating, following which a reflex transfer film cut to the contour of the pattern is positioned with the reflecting side inwards against the elastomer treated plastisol print and adhered to it by brief heating under a quite slight pressure. The thus formed plastisol reflex transfer may then be transferred to the desired substrate, in particular a textile, by conventional heat application. By this means it is possible to decorate textiles or other, preferably flexible, materials with patterns consisting of strongly light reflecting areas delimited by coloured areas without having to cut out each light reflecting detail separately. However, manual work is still demanded for punching or cutting out the more regular pieces of reflex transfer film which are coupled onto the conventional plastisol transfer, and the light reflecting details must at least partially be delimited by coloured areas.
U.S. Pat. No. 4,102,562 discloses a transfer sheet material for forming retro-reflective graphic images on a substrate, said sheet material comprising a support sheet, a dense continuous monolayer of transparent microspheres partially and removably embedded in the support sheet to a depth averaging between about one-quarter and one-half of their diameter, a specularly reflective layer covering the surfaces of the microspheres which are exposed above the support sheet, and a transfer layer printed over the layer of microspheres in an imagewise pattern, which leaves areas of the layer of microspheres without pattern, the transfer layer being of a thickness such as to embed within it the surfaces of the microspheres that are exposed above the support sheet in the printed areas, and the transfer layer being adhereable to a substrate while retaining its imagewise pattern so that when the transfer layer is adhered to the substrate and the support sheet is stripped away, the transfer layer is left in place on the substrate, with the microspheres pulled from the support sheet and partially embedded in the transfer layer to form an image which is retro-reflective over its full area. It is also stated that the transfer layer consists of a vinyl plastisol ink, and that the specularly reflective layer on the microspheres consists of a transparent dielectric mirror, but may also, if transparency is not necessary, consist of a vapor-coated metal, such as aluminium. It is further stated that a thin adhesion promoting layer comprising a polyurethane or a silane may be disposed between the specularly reflective layer and the transfer layer.
It has however been found that transfer layers of this kind, even when an adhesion promoting layer is applied between the specularly reflective layer and the transfer layer, do not ensure sufficient adhesion of the microspheres and do not adhere sufficiently to flexible substrates, such as textiles. Thus it is seen from example 1 of U.S. Pat. No. 4,102,562 that a reflecting image transferred onto garment from a transfer according to that patent specification lost 60% of its retro-flective intensity already after 5 washes in an automatic washer using hot water. Besides, images based on vinyl plastisol inks cannot stand dry cleaning. These drawbacks must be the reason why this kind of reflex transfer has not been put into practical use since it was invented in 1976.